An annual, coarse, rough herb of seashores and river beaches, with rough, purplish or blotched stems, 1 to 2 feet high. Leaves alternate, tough, coarse, very rough with scattered, short, papillose hairs and obscurely toothed and more or less lobed. Inflorescence rather small, consisting of heads of greenish discoid flowers, the staminate ones clustered in heads at the ends of the branches, the pistillate or fertile flowers axillary in the upper leaves. Flowers of the staminate heads with tubular corollas; the pistillate heads consisting of an ovoid or oblong closed involucre covered with hooked spines, with no corolla or pappus. Fruit a prickly bur, usually several clustered in the axils of the leaves, ovoid to oval, one-half to two-thirds of an inch long and one-third to one-half of an inch thick, covered with hooked prickles, and densely hairy with reddish hairs, the summit of the bur bearing two stout, hispid, incurving clawlike beaks, the interior of the bur two-celled, each cavity containing one obovoid or oblong achene.
Memoir 15 N. Y. State Museum
B. Beach Clotbur - Xanthium echinatum
On sea beaches, lake and river shores, and occasionally in waste ground, Nova Scotia to North Carolina, west to Minnesota and North Dakota. In New York found mainly in sandy soil and on beaches of Long Island and Staten Island, the Great Lakes and a few inland localities.
Flowers appear in July and August and the bur is ripe in September or October.
The Common Cocklebur or Clotbur (Xanthium canadense Miller) is a common weed almost everywhere. It resembles the one illustrated here, but is usually larger in every way, the beaks of the bur being almost straight and more or less divergent.
The Clotburs (Xanthium) are usually placed in the Ragweed family iAmbrosiaceae) but here retained for convenience in the Sunflower family.